gulp-angular-filesort is a Gulp plugin that automatically sorts AngularJS application files based on module definitions and usage, helping to prevent common dependency errors like `Uncaught Error: [$injector:modulerr]`. It's designed for developers using AngularJS with Gulp, particularly those using `gulp-inject` to manage script dependencies in their build process. The tool is specifically useful for existing AngularJS projects but the repository maintainers recommend using modern alternatives like Browserify or Webpack for new applications.